Grid-controlled gaseous discharge device



NOV. 11, 1952 P, W, STUTSMAN 2,617,958

GRID-CONTROLLED GASEOUS DISCHARGE DEVICE Filed Sept. l, 1949 #7mm/Ey Patented Nov. 11, 1952 Gain-componen GAsEoUsfnisicHARGE DEVICE Paul W. Stutsman, Needham,l Massi', assigner to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application September l, 1949,`Serial` No. 113,551

3 Claims. (Cl. 313-250)- This application relates to electron discharge devices and more particularly to gaseous discharge devices of the grid control type.

In applicants copending application, Serial No. 57,533, filed October 30, 1948, there is disclosed a gaseous discharge device of the cold cathode type capable of passing high peak currents on the order of 100 amperes, said discharge device being built in a metal envelope of normal size. It has become desirable to devise a means of producing a tube of this general type in a miniature bulb. Applicant has discovered that the grid and cathode may be firmly and rigidly supported by positioning an insulating member between them and urging this assembly together. By so doing, at least one of the grid support members may be eliminated and a more rugged and accurately positioned device may be produced. This device may then be reduced to a suitable size for insertionl into the miniature bulb without detracting from the ruggedness of the construction. This vstructure taken in conjunction with a shielded anode member will produce a device capable of passing high peak currents. A high forward voltage may be obtained by adjustment of the Spacing between the grid and cathode to a distance less than the minimum breakdown distance for the gas and pressure used. A high inverse peak voltage is possible due to the relatively large spacing between the anode and cathode. A short deionizing time is produced by the limited cross section of the discharge path and the large area surrounding said path for collecting ionized gas components.

The means of producing a device having these and other advantages will be apparent to persons skilled in the art as the description thereof progresses, reference being had to the accompanying drawings wherein: Y

Fig. l illustrates a, longitudinalV cross-sectional View of the device embodying this invention taken along line I -I of Fig. 2; and

Figs. 2 and 3 are transverse cross-sectional views of the species shown in Fig. l taken along lines 2-2 and 3-3, respectively, of Fig. 1.

Referring now to Fig. l, there is shown an envelope Ill having a glass button Il sealing its lower end. The upper end of envelope I is closed by a glass` seal I2 through which extends a conducting member I3. Attached to conducting member I3 is a metal cap Ill which is rigidly held to member I3, for example, by a quantity of solder I5. The cap I4 is rmly held to the glass sealing member I2 by a mass of glue I6.

The lower end of rod I3 which extends downwardly inside envelope I0 is attached to an anode member I1 comprising a short rod of carbon whose diameter is substantially equal to the diameter of member I3. The attachment of anode member l1 to member I3 is accomplished by a short metallic sleeve I8 surrounding andV frictionally engaging the lower end of conducting member I3 and the upper end of cathode I'I.

Surrounding conducting member I3 and anode member II is a metallic shield member I9 comprising a cylinder whose Ilower end extends into envelope I0 for substantially the same distance as carbon button I'I and whose upper end is imbedded in the glass sealing member l2. The sleeve I9 does not touch the sleeve I8, the carbon rod I'I, or conducting member I3.

Surrounding thershield member I9 is a dielectricshield 20 comprising a glass tube fused to seal I-2 and extending down into envelope I0 for the length of metallic shield I9.

Surrounding the dielectric shield Zis a tubular grid member 2l, which may be, for example, of carbon, whose upper end is in close proximity with but not touching the glass seal I2 and the dielectric shield 20, and whose lower end extends downward into envelope I0 for approximately twice the length of dielectric shield 20. The recess in grid member 2 I, which accommodates the anode structure and its accompanying shields, extends downward with a uniform diameter from the top thereof to a point somewhat below the end of shield member 20, for example, approximately one diameter of sleeve I8 therebelow. The diameter of the recess is then reduced to a diameter which may be, for example, approximately equal to the inside diameter of shield 20 and extends the remainder of the length of grid member 2I. Surrounding grid member 2I is a ceramic member 22 in contacting engagement therewith from a point adjacent the lower end of conducting member I3- downward to the lower end of grid member 2|. The ceramic member 22 extendsdownward beyond the lower end of grid member 2I for a distance approximately equal to the radius of envelope I0. The recess which accommodates grid member 2| is substantially reduced below the lower end of said grid member such that the hole in the ceramic member 22 at the lower end of grid member 2| is slightly less than the diameter of the recess in the lower end of grid member 2 I.

A t a point somewhat below the lower end of gridmember 2I for example, one diameter of the shieldV member I9 therebelow, the recess in ceramic member 22 is again enlarged to accommodate a cathode comprising a tubular member 23 which snugly ts in saidenlarged recess, the diameterv of saidr recess being slightly smaller than the outside diameterof grid member 2l.V The upper 'end of tubular member 23 is curved inward to form a substantially closed end, except for van aperture 24 in the center thereof, the diameter of said aperture being slightly smaller than the diameter of conducting member I3.

Inside tubular member 23 is packed electron emissive material 25 of any desired type such as, for example, a iinely divided mixture of aluminum and caesium chloride. The lower end of tubular member 25 is sealed by a metallic member 25' attached to the walls thereof as by welding. Attached to the lower end member 25 is a plurality of leads 26 which extend through the glass button l I to provide conducting lead-in members and are of sucient stiffness to rigidly support the cathode.

The upper end of the cathode grid assembly is rigidly positioned by a mica spacer 21 comprising a ring-like member Whose inner diameter is equal to the outer diameter of grid member 2l and firm- 1y engages said grid member. The outer diameter of mica spacer 21 is equal to the inside diameter of envelope IE) such'that the outer surface of the mica spacer rmly engages the inner walls of envelope Ii). The mica spacer rests on the upper end of ceramic member 22 and is rigidly urged against said ceramic member by a metallic strap 28 surrounding grid member 2i above mica spacer 21. Attached to strap 2S Yis a lead-in member 29 which extends downward through holes in mica spacer 21 and ceramic member 22 and through a ceramic bushing 30 positioned below insulating member 22, and thence through the sealing button l l. The upper end of the ceramic bushing 3@ is accommodated by a recess in ceramic member 22 and the lower end of said bushing is firmly held f to the inner surface of sealing button ll by a ceramic glue 3 I Thus it may be seen that the mica spacer, grid, ceramic member 22 and cathode are all rigidly maintained in stacked relationship by the tension of the lead-in member 29 whereby both longitudinal and transverse movement between these elements is prevented. Since this assembly is rigidly positioned with respect to the envelope I2 by means of the spacer 21 and lead-in members 26 and ceramic sleeve 3H, the relative position of this assembly to the anode assembly which is attached to the-upper end of envelope It] is maintained.

Extending transversely through ceramic member 22 and grid member 2l such that it intersects the axis of the recesses in these members is a hole 32 thereby connecting the passage between the anode and cathode with the other spaces existing in the device. When the tube lires, this central passage between the anode and cathode is heated by the discharge such that gaseous material moves outwardly through hole 32 carrying electron emissive material eroded from the cathode with it. By this action a substantial amount of electron emissive material is prevented from condensing on the grid and anode members such that the high forward and inverse voltages of the tube are not reduced as would be the case if electron emissive material were deposited on the anode and grid surfaces.

The tube may be filled with any desired gas such as, for example, helium at 12 millimeters of pressure. Also, a small quantity of Water vapor may be added for the purpose of increasing operational characteristics as is morev completely described in the aforementioned copending application. In operation a positive potential applied to the grid member 2i with respect to the cathode causes electrons to be attracted from the exposed upper surface of the cathode tube 23. These electrons strike gas molecules to ionize the same and createv positive ions, Which then fall back through the aperture 24 to bombard the electron emissive material 25, thereby producing a supply of electrons which are attracted out through aperture 24 by the positive potential in grid 24 Iand which pass to the anode l1 to fire the tube.

This completes the description of the particular embodiment of the invention disclosed herein. However, many modifications thereof will be apparent to persons skilled in the art. For example, different types of cathode may be used and the envelope I!) could be metallic instead of glass. Therefore, applicant does not wish to be limited to the particular details of the species described herein except as dened by the appended claims.

What is claimed is:

1. A gaseous discharge device comprising a cathode, an anode, a grid, and 'an insulating member positioned between and engaging said cathode and said grid, said cathode comprising a tubular member containing electron emissive material, a portion of the outer surface of said tubular member engaging an inner surface of `a recess in said insulating member, said grid comprising a cylindrical member, the outer surface of said cylindrical member engaging an inner surface of a recess in said insulating member, and means for iirmly urging said cathode and said grid into said recesses. v

2. A gaseous discharge device comprising a cathode, an anode, a grid, an insulating member positioned between and engaging said cathode and said grid, said cathode comprising a tubular member containing electron emissive material, the outer surface of said tubular member engaging the inner surface of a recess in said insulating member, said grid comprising a cylindrical member, the outer surface of said cylindrical member engaging an inner surface of a recess in said insulating member, and means for rmly urging said cathode and said grid into said recesses comprising a base member attached to said cathode and to said grid member.

' 3. A gaseous discharge device comprising a cathode, an anode, a grid, an insulating member positioned between and engaging said cathode and said grid, said cathode comprising a tubular member containing electron emissive material, the cuter surface of said tubular member engaging the inner surface of a recess in said insulating member whereby transverse motion between said cathode and said grid is prevented, said grid comprising a cylindrical member, the outer surface of said cylindrical member engaging an inner sur- Vface of -a recess in said insulating member Whereby transverse movement between said grid and said insulating member is substantially prevented, and means for firmly urging said cathode and said grid into said recesses comprising a base member supportingly attached to said cathode and to said grid member.

' vPAUL W. STUTSMAN.

REFERENCES CTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Dato 1,714,402 Smith May 21, 1929 1,917,732 Schroter July 11, 1933 2,202,588 Kniepkamp May 28, 1940 2,433,813 Hilliard Dec. 3), 1947 2,496,825 Szegho Feb. 7, 1950 

